The present invention relates to a method for lining the inner surfaces of pipes in a multibranch piping.
Heretofore, as means for lining the inner surfaces of pipes in a multibranch piping there have been proposed such methods as disclosed in Japanese Patent Laid-Open Nos. 175579/85 and 175580/85 and Japanese Patent Publication Nos. 8233/87, 55911/87, 10707/87 and 26830/87.
According to the method described in the above Japanese Patent Laid-Open No. 175579/85, in such a multibranch piping as shown in FIG. 6, a coating material and then air are fed from a start end 6 of a main pipe 1, then upon detection that the coating material reached ends 11A, 11B and 11C of branch pipes 10A, 10B, 10C, respectively, the ends 11A, 11B and 11C are closed successively to complete the lining of the branch pipes 10A, 10B, 10C, while the lining operation is continued for the main pipe 1 until the coating material reaches a terminal end 2 of the main pipe.
According to the lining method described in Japanese Patent Laid-Open No. 175580/85, air is fed back from pipe ends 11 at which a coating material has arrived in the same manner as in the method of the foregoing Laid-Open No. 175579/85.
According to the lining method described in Japanese Patent Publication No. 8233/87, a coating material and then air are fed from the start end 6, and when the coating material has reached the end 11A of the branch pipe 10A, the amount of air fed from the start end 6 is decreased and at the same time air is fed back from the end 11A to send back the coating material.
According to the lining method described in Japanese Patent Publication No. 55911/87, a coating material and then air are fed from the start end 6 and it is detected by a pressure gauge mounted in the end 11A of the branch pipe 10A that the coating material has reached a branch point 12A, whereupon the air fed from the start end 6 is stopped, then the coating material and air are fed from the end 11A to effect a lining for the inner surface of the branch pipe 10A and that of the main pipe 1 which follows.
According to the lining method described in Japanese Patent Publication No. 10707/87, a coating material and then air are fed from the ends 11A, 11B and 11C of the branch pipes 10A, 10B and 10C, respectively, and it is detected that the coating material has reached branch points 12A, 12B and 12C, by measuring a change in pressure of the compressed air fed into the pipes, to complete the lining operation.
According to the lining method described in Japanese Patent Publication No. 26830/87, there are adopted different lining start timings for the branch pipes 10A, 10B and 10C so that the lining operations for those pipes are completed simultaneously.
The methods described in the above Japanese Patent Laid-Open Nos. 175579/85, 175580/85 and Publication No. 8233/87 are each disadvantageous in that (1) when the coating material is fed continuously, the main pipe 1 is coated repeatedly, resulting in the lining of the main pipe becoming too thick, and (2) where the coating material is fed batchwise at a time, even when the coating material has reached the end 11A of the branch pipe 10A there still remain in the main pipe 1 a large amount of the coating material for lining the other pipes, and also in the branch pipe 10A there is a surplus of the coating material, so it is necessary to feed air back from the end 11A of the branch pipe 10A to return the surplus coating material in the branch pipe 10A into the main pipe 1. Thereafter, the coating material in the main pipe 1 is fed to the branch pipe 10B and these operations are repeated successively, so that the branch pipes 10A, 10B and 10C are twice-coated, that is, the total lining time becomes longer. Consequently, it is difficult to complete the lining within the pot life of the coating material.
In the method described in the above Japanese Patent Publication No. 55911/87, the change in pressure is of a very small value. So in order to prevent the operator from overlooking such a pressure change it is necessary to monitor the pressure gauge, concentrating the attention of the operator thereon at all times. But this is very difficult in a working site frequented by a large number of people. Means for monitoring which employ a recorder is disadvantageous in that the equipment cost is high.
In the method described in the above Japanese Patent Laid-Open No. 10707/87, the measurement of a pressure change would be next to impossible without an automatic recorder. The use of an automatic recorder leads to an increase in cost.
In the method described in the above Japanese Patent Publication No. 26830/87, the time required for lining each of the branch pipes 10A, 10B and 10C is calculated before the lining operation. But the time required for the lining operation is influenced by various factors such as the temperature of the coating material, the flow velocity of the air being fed and the temperature thereof. So even if such time is calculated beforehand, it involves a large error, making it impossible to effect the lining operation to a satisfactory extent. Performing the lining operation with a certain time delay is also difficult in working sites where there are complicated passages.
Where the main pipe 1 is very long, for example, in case of a main pipe 20 mm or so in bore and 20 m or more in length, it will take a long period of time for lining the main pipe 1 and so it becomes difficult to complete the lining operation within the pot life of the coating material.